Kenya's military controls half of the Somalian port city of Kismayo as it tries to drive out the al Qaeda-linked militant group Al-Shabaab from one of its last strongholds, a military spokesman said Saturday.

Kenyan and Somali ground forces are in control of the northern part, which is the old city, after a day and a half of fighting, spokesman Cyrus Oguna told CNN.

They are consolidating the areas they have gained before moving into the south, where the Islamic militant group is believed to be, he said. The military launched airstrikes against the group Saturday.

"Al-Shabaab has not been able to offer any resistance whatsoever to the ground forces since the ground forces landed there yesterday, and the whole of yesterday and the good part of today they have (suffered) heavy casualties," Oguna said.

The Kenya Defense Forces inflicted "massive destruction" on Al-Shabaab's infrastructure Saturday, using jets and helicopter gunships to destroy three of the group's bases, according to the military's official Twitter account. "Great care and caution has been exercised to avoid collateral damage," it said.

Kenya's military makes up the majority of troops in an African Union offensive to drive Al-Shabaab out of Somalia, where the group has long tried to overthrow the government.

Al-Shabaab has suffered setbacks in the fight, including losing control of much of the capital, Mogadishu, last year. That made Kismayo even more critical for the group, which uses the port to profit from the illegal charcoal trade and smuggling operations.